102 STUDIES OF NATURE. 



greateft part of two vafl: Continents ? Our fyftems, 

 therefore, cannot account for the fteepy elevation 

 of mountains of granite, by any kind of degrada- 

 tion, becaufe they know not how to difpofe of the 

 fragments J nor for the formation of calcareous 

 mountains, by the movements of the Ocean, be- 

 caufe, in it's adual flate, it is incapable of cover- 

 ing them. 



Befides, it is not an opinion of yefterday, that 

 Philofophers have confidered the Earth as a de- 

 caying edifice. Hear what Baron Bii/heqiiius fays 

 of the opinion of Polybius, in his curious and en- 

 tertaining letters : " Polybiiis pretends to have 

 " proved, that the entrance of the Black Sea 

 ** would, in procefs of time, be choked by the 

 " banks of fand, and by the mud, which the Da- 

 ** nube and the Boriflhenes were conftantly forcing 

 " into it : and that, confequently, the Black Sea 

 " would be rendered inacceffible, and it's com- 

 " merce entirely deftroyed. The fea of Pontus, 

 " neverthelefs, is juft as navigable at this hour as 

 ** in the days of Polybiiis *." 



Bays, gulfs, and mediterranean feas, are no more 

 the effedts of irruptions of the Ocean into the 

 Land, than mountains are produftions of the cen- 



* Letter I. page 131. 



trifugal 



